Previously, Rust-Oleum Corp. purchased a distillation unit from Progressive Recovery to recycle the solvents used in their manufacturing process. As their manufacturing volume increased and their solvent waste stream changed, they found the original unit was not able to keep up with their recovery needs. Ten years later expenses for off-site disposal and recovery were in excess of $250,000 and represented an area of significant potential savings.
A review of the solvent used and recovery operation found that Rust-Oleum was generating a blend of dirty solvents at the rate of 1,250 to 2,000 gallons per day with solids consisting primarily of pigments and resins varying from 15-30% of the volume. The dirty solvent that could not be recycled was being re-mixed with the ‘still’ bottoms and sent to an off-site recovery service using a thin film evaporator. Additionally, low boiling solvents, like acetone, were flashing, foaming, and carrying over solids contaminating the clean solvent.
Another concern was that the two part epoxy or polyurethane paint wastes could accidentally be introduced into the ‘still’ where heat would accelerate the catalyzing process and cause cross-linking and solidification of the mass. To clean the ‘still’, the solid mass would have to be broken up and removed in pieces from the distillation chamber. On multiple occasions, significant damage from solidification was done to the ‘still’ requiring extensive repair of the unit.
Rust-Oleum saw the need and was considering a method to maximize their solvent recovery, minimize their virgin solvent purchases and reduce associated maintenance costs. Two key employees, the Environmental Engineering Manager and Engineering Project Manager were selected and headed a committee assigned to research the possible alternative. After evaluating other potential vendors, they partnered with PRI to implement the solutions PRI offered. Before any hardware was selected, a thorough needs assessment was conducted, and a series of software distillation simulation models were performed. Upon engineering review, a unit design was selected for Rust-Oleum’s consideration. PRI recommended an SCR series scraped surface distillation system with the Performance Process Control package (PPC), Form Suppression, and Sludge Transfer system.
A model SC-550E was modified to include an external heat source that generated the energy required for high volume recovery while maintaining a high degree of control and permitting the foam suppression package to function in a smooth, controlled manner. The PPC package automatically monitors the still’s operation to assure maximum throughput and a consistent ‘still’ bottom. As recovery rate degradation occurs or a tendency toward solidification is detected, the system calls for an immediate, safe discharge of the ‘still’ contents to the sludge holding tank. The Sludge Transfer system provides a quick, positive sludge pump-down, and includes a method to flush the line between the ‘still’ and the sludge holding tank to minimize the possibility of solids build-up in the sludge transfer line.
In addition, the system ’s display delivers real-time information regarding the systems’ operational status. If a problem occurs, an alarm is given and is flashed on the screen and the operator is directed to the systems troubleshooting and diagnostics menu for guidance. A modulated vacuum and surge tank system provides recovery of low boiling solvents at higher rates without choking the vacuum pump and causing overheating problems. An oversized 30” manway was also included for easier vessel access to inspect or to perform maintenance
This SCR-550E was not an “off-the-shelf” distillation unit but an example of how a standard unit can be modified for high volume recovery of a difficult blend of solvents and solids. This advanced hardware and software package provides a high throughput rate and assures clean, clear solvent while minimizing the potential for ‘still’ solidification. Besides the obvious economic savings, Rust-Oleum has reduced the number of hazardous wastes leaving their site and the associated liabilities in transportation, storage, or disposal. The new solvent recovery system from Progressive Recovery is definitely a beneficial addition to Rust-Oleum’s Pleasant Prairie operations.